When a TSV (through substrate via) is filled with a material that has a coefficient of thermal expansion (CTE) mismatch relative to its substrate (e.g., silicon), the TSV incurs high compressive stress. In particular, the compressive stress may be transmitted through the surrounding substrate to neighboring devices. The transferred compressive stress may cause a shift in the parameters of the devices that surround the TSV.
Conventional techniques for addressing compressive stress include a “Keep-Out Region” surrounding the TSV. The Keep-Out Region defines an area surrounding the TSV in which sensitive devices cannot be placed. Unfortunately, a Keep-Out Region results in a circuit layout area penalty. For example, a Keep-Out Region can be as large as five to ten micro-meters (5-10 um) in radius, depending on the particular device sensitivity.
Copper is an example of a filling material that has a CTE mismatch to silicon. When a TSV confined by silicon is thermal cycled, the copper filling material within the TSVs may expand upwardly and out of the TSV. The pumping of the copper upwardly and out of the TSV may disrupt any circuits near the TSV. Although described with reference to copper, the expansion of any filling material that has a CTE mismatch with respect to its substrate, when used to fill a TSV, causes the above-noted problems.